A combination of three phenomena is increasingly threatening ecosystems in the southern and equatorial regions of the Atlantic ocean—marine heat waves, high acidification, and low chlorophyll concentration.
Before 2016, it was unusual for these factors to converge. Since then, they have been observed simultaneously every year. All three phenomena stem from the current climate emergency.
The ocean is among the planet’s main climate regulators. It absorbs some 90 percent of the heat from the atmosphere and 30 percent of the carbon dioxide. When atmospheric heat is excessive, the ocean overheats. The accumulation of carbon dioxide makes the water more acidic.
These events could be alleviated if the food supply for marine species were adequate. Some ecosystems are able to survive warmer, more acidic waters if food is available.
However, with very warm waters, there are fewer gases that serve as nutrients for microscopic algae—the basis of the ocean’s food chain. This raises the risk of mortality for marine species and damages the sustainability of fishing and marine farming.
The increased occurrence of these three drivers makes it impossible for ecosystems to recover, as a minimum amount of time is required for regeneration to take place.
The study
The study was published in the journal Nature Communications and was carried out by researchers from the Federal University of Santa Catarina (UFSC) and the National Institute for Ocean Research (INPO).
The data cover 1999 through 2018 and were collected using research satellites. Six regions of the South Atlantic were evaluated, considering their high biodiversity and biological productivity.
The locations studied are the Western Equatorial Atlantic (near the coast of the Brazilian Northeast), the Western Subtropical Atlantic, the Brazil-Malvinas Confluence, the Gulf of Guinea, the Angola Front, and the Agulhas Current (which connects the Atlantic and Indian Oceans).
These areas are believed to account for the fishing of eight million tons of marine life per year, which support coastal communities in South America and Africa. The food security of South American and African countries is directly impacted.
Researcher Regina Rodrigues, from UFSC and INPO, says that research into these phenomena can help build policies and make more well-informed decisions about the oceans.
“Marine ecosystems are under pressure from different types of pollution—chemical waste, agricultural waste, pesticides, and untreated sewage, not to mention illegal fishing, which occurs at a faster rate than species can reproduce. We should make more conservation areas and regulations to take these pressures off ecosystems. The warming and the acidity of the sea cannot be tackled now; they require broader measures to reduce greenhouse gases,” she declared.
Source: Agência Brasil